1. The Field of the Invention
Implementations of the present invention relate generally to drilling devices and methods that may be used to drill geological and/or manmade formations. In particular, implementations of the present invention relate to core barrel assemblies.
2. The Relevant Technology
Core drilling (or core sampling) includes obtaining core samples of subterranean formations at various depths for various reasons. For example, a retrieved core sample can indicate what materials, such as petroleum, precious metals, and other desirable materials, are present or are likely to be present in a particular formation, and at what depths. In some cases, core sampling can be used to give a geological timeline of materials and events. As such, core sampling may be used to determine the desirability of further exploration in a particular area.
Wireline drilling systems are one common type of drilling system for retrieving a core sample. In a wireline drilling process, a core drill bit is attached to the leading edge of an outer tube or drill rod. A drill string is then formed by attaching a series of drill rods that are assembled together section by section as the outer tube is lowered deeper into the desired formation. A core barrel assembly is then lowered or pumped into the drill string. The core drill bit is rotated, pushed, and/or vibrated into the formation, thereby causing a sample of the desired material to enter into the core barrel assembly. Once the core sample is obtained, the core barrel assembly is retrieved from the drill string using a wireline. The core sample can then be removed from the core barrel assembly.
Core barrel assemblies commonly include a core barrel for receiving the core, and a head assembly for attaching the core barrel assembly to the wireline. Typically, the core barrel assembly is lowered into the drill string until the core barrel reaches a landing seat on an outer tube or distal most drill rod. At this point a latch on the head assembly is deployed to restrict the movement of the core barrel assembly with respect to the drill rod. Once latched, the core barrel assembly is then advanced into the formation along with the drill rod, causing material to fill the core barrel.
One potential challenge can arise due to the interaction between the core barrel assembly and the drill string. For example, when the drill string is spinning, the inertia of the core barrel assembly can exceed the frictional resistance between the mating components such that the head assembly rotates at a lower rate than the drill rod or fails to rotate and remains stationary. In such a situation, the mating components can suffer sliding contact, which can result in abrasive wear.
Often it may be desirable to obtain core samples at various depths in a formation. Furthermore, in some cases, it may be desirable to retrieve core samples at depths of thousands of feet below ground-level, or otherwise along a drilling path. In such cases, retrieving a core sample may require the time consuming and costly process of removing the entire drill string (or tripping the drill string out) from the borehole. In other cases, a wireline drilling system may be used to avoid the hassle and time associated with tripping the entire drill string. Even when using a wireline drilling system, tripping the core barrel assembly in and out of the drill string is nonetheless time-consuming.
Accordingly, there are a number of disadvantages in conventional wireline systems that can be addressed.